lfsr: Add support for non-self-synchronizing scrambler, add tests for PCIe gen 1/2 scrambler

Signed-off-by: Alex Forencich <alex@alexforencich.com>

src/lfsr/rtl/taxi_lfsr.sv

@@ -169,6 +169,7 @@ PRBS23      Fibonacci, inverted     23      23'h040001      any             ITU
 PRBS29      Fibonacci, inverted     29      29'h08000001    any
 PRBS31      Fibonacci, inverted     31      31'h10000001    any
 64b66b      Fibonacci, bit-reverse  58      58'h8000000001  any             10G Ethernet
+pcie        Galois, bit-reverse     16      16'h0039        16'hffff        PCIe gen 1/2
 128b130b    Galois, bit-reverse     23      23'h210125      any             PCIe gen 3
 
 */

src/lfsr/rtl/taxi_lfsr_descramble.sv

@@ -28,7 +28,9 @@ module taxi_lfsr_descramble #
     // bit-reverse input and output
     parameter logic REVERSE = 1'b1,
     // width of data bus
-    parameter DATA_W = 64
+    parameter DATA_W = 64,
+    // self-synchronizing
+    parameter logic SELF_SYNC = 1'b1
 )
 (
     input  wire logic               clk,
@@ -141,6 +143,7 @@ PRBS23      Fibonacci, inverted     23      23'h040001      any             ITU
 PRBS29      Fibonacci, inverted     29      29'h08000001    any
 PRBS31      Fibonacci, inverted     31      31'h10000001    any
 64b66b      Fibonacci, bit-reverse  58      58'h8000000001  any             10G Ethernet
+pcie        Galois, bit-reverse     16      16'h0039        16'hffff        PCIe gen 1/2
 128b130b    Galois, bit-reverse     23      23'h210125      any             PCIe gen 3
 
 */
@@ -157,14 +160,14 @@ taxi_lfsr #(
     .LFSR_W(LFSR_W),
     .LFSR_POLY(LFSR_POLY),
     .LFSR_GALOIS(LFSR_GALOIS),
-    .LFSR_FEED_FORWARD('1),
+    .LFSR_FEED_FORWARD(SELF_SYNC),
     .REVERSE(REVERSE),
     .DATA_W(DATA_W),
-    .DATA_IN_EN(1'b1),
+    .DATA_IN_EN(SELF_SYNC),
     .DATA_OUT_EN(1'b1)
 )
 lfsr_inst (
-    .data_in(data_in),
+    .data_in(SELF_SYNC ? data_in : '0),
     .state_in(state_reg),
     .data_out(lfsr_data),
     .state_out(lfsr_state)
@@ -173,7 +176,7 @@ lfsr_inst (
 always_ff @(posedge clk) begin
     if (data_in_valid) begin
         state_reg <= lfsr_state;
-        output_reg <= lfsr_data;
+        output_reg <= SELF_SYNC ? lfsr_data : (lfsr_data ^ data_in);
     end
 
     if (rst) begin

src/lfsr/rtl/taxi_lfsr_scramble.sv

@@ -28,7 +28,9 @@ module taxi_lfsr_scramble #
     // bit-reverse input and output
     parameter logic REVERSE = 1'b1,
     // width of data bus
-    parameter DATA_W = 64
+    parameter DATA_W = 64,
+    // self-synchronizing
+    parameter logic SELF_SYNC = 1'b1
 )
 (
     input  wire logic               clk,
@@ -141,6 +143,7 @@ PRBS23      Fibonacci, inverted     23      23'h040001      any             ITU
 PRBS29      Fibonacci, inverted     29      29'h08000001    any
 PRBS31      Fibonacci, inverted     31      31'h10000001    any
 64b66b      Fibonacci, bit-reverse  58      58'h8000000001  any             10G Ethernet
+pcie        Galois, bit-reverse     16      16'h0039        16'hffff        PCIe gen 1/2
 128b130b    Galois, bit-reverse     23      23'h210125      any             PCIe gen 3
 
 */
@@ -160,11 +163,11 @@ taxi_lfsr #(
     .LFSR_FEED_FORWARD('0),
     .REVERSE(REVERSE),
     .DATA_W(DATA_W),
-    .DATA_IN_EN(1'b1),
+    .DATA_IN_EN(SELF_SYNC),
     .DATA_OUT_EN(1'b1)
 )
 lfsr_inst (
-    .data_in(data_in),
+    .data_in(SELF_SYNC ? data_in : '0),
     .state_in(state_reg),
     .data_out(lfsr_data),
     .state_out(lfsr_state)
@@ -173,7 +176,7 @@ lfsr_inst (
 always_ff @(posedge clk) begin
     if (data_in_valid) begin
         state_reg <= lfsr_state;
-        output_reg <= lfsr_data;
+        output_reg <= SELF_SYNC ? lfsr_data : (lfsr_data ^ data_in);
     end
 
     if (rst) begin

src/lfsr/tb/taxi_lfsr_descramble/Makefile

@@ -36,6 +36,7 @@ export PARAM_LFSR_INIT ?= "'1"
 export PARAM_LFSR_GALOIS ?= "1'b0"
 export PARAM_REVERSE ?= "1'b1"
 export PARAM_DATA_W ?= 8
+export PARAM_SELF_SYNC ?= "1'b1"
 
 ifeq ($(SIM), icarus)
 	PLUSARGS += -fst

src/lfsr/tb/taxi_lfsr_descramble/test_taxi_lfsr_descramble.py

@@ -76,7 +76,21 @@ def descramble_64b66b(data, state=0x3ffffffffffffff):
     return data_out
 
 
-async def run_test_descramble(dut, ref_scramble):
+def scramble_pcie(data, state=0xffff, poly=0x9c00):
+    data_out = bytearray()
+    for d in data:
+        b = 0
+        for i in range(8):
+            if state & 1:
+                state = (state >> 1) ^ poly
+                b = b | (1 << i)
+            else:
+                state = state >> 1
+        data_out.append(b ^ d)
+    return data_out
+
+
+async def run_test_descramble(dut, ref_scramble, ref_descramble):
 
     data_width = len(dut.data_in)
     byte_lanes = data_width // 8
@@ -87,9 +101,9 @@ async def run_test_descramble(dut, ref_scramble):
 
     block = bytearray(itertools.islice(itertools.cycle(range(256)), 1024))
 
-    scr = scramble_64b66b(block)
+    scr = ref_scramble(block)
 
-    dscr = descramble_64b66b(scr)
+    dscr = ref_descramble(scr)
 
     assert dscr == block
 
@@ -122,7 +136,12 @@ if cocotb.SIM_NAME:
     # if cocotb.top.LFSR_POLY.value == 0x8000000001:
     if int(cocotb.top.LFSR_W.value) == 58:
         factory = TestFactory(run_test_descramble)
-        factory.add_option("ref_scramble", [scramble_64b66b])
+        factory.add_option(("ref_scramble", "ref_descramble"), [(scramble_64b66b, descramble_64b66b)])
+        factory.generate_tests()
+
+    if cocotb.top.LFSR_POLY.value == 0x0039:
+        factory = TestFactory(run_test_descramble)
+        factory.add_option(("ref_scramble", "ref_descramble"), [(scramble_pcie, scramble_pcie)])
         factory.generate_tests()
 
 
@@ -145,11 +164,13 @@ def process_f_files(files):
     return list(lst.values())
 
 
-@pytest.mark.parametrize(("lfsr_w", "lfsr_poly", "lfsr_init", "lfsr_galois", "reverse", "data_w"), [
+@pytest.mark.parametrize(("lfsr_w", "lfsr_poly", "lfsr_init", "lfsr_galois", "reverse", "data_w", "self_sync"), [
-            (58,  "58'h8000000001", "'1", 0, 1, 8),
+            (58,  "58'h8000000001", "'1", 0, 1, 8, 1),
-            (58,  "58'h8000000001", "'1", 0, 1, 64),
+            (58,  "58'h8000000001", "'1", 0, 1, 64, 1),
+            (16,  "16'h0039", "'1", 1, 1, 8, 0),
+            (16,  "16'h0039", "'1", 1, 1, 64, 0),
         ])
-def test_taxi_lfsr_descramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois, reverse, data_w):
+def test_taxi_lfsr_descramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois, reverse, data_w, self_sync):
     dut = "taxi_lfsr_descramble"
     module = os.path.splitext(os.path.basename(__file__))[0]
     toplevel = dut
@@ -169,6 +190,7 @@ def test_taxi_lfsr_descramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois
     parameters['LFSR_GALOIS'] = f"1'b{lfsr_galois}"
     parameters['REVERSE'] = f"1'b{reverse}"
     parameters['DATA_W'] = data_w
+    parameters['SELF_SYNC'] = f"1'b{self_sync}"
 
     extra_env = {f'PARAM_{k}': str(v) for k, v in parameters.items()}
 

src/lfsr/tb/taxi_lfsr_scramble/Makefile

@@ -36,6 +36,7 @@ export PARAM_LFSR_INIT ?= "'1"
 export PARAM_LFSR_GALOIS ?= "1'b0"
 export PARAM_REVERSE ?= "1'b1"
 export PARAM_DATA_W ?= 8
+export PARAM_SELF_SYNC ?= "1'b1"
 
 ifeq ($(SIM), icarus)
 	PLUSARGS += -fst

src/lfsr/tb/taxi_lfsr_scramble/test_taxi_lfsr_scramble.py

@@ -64,6 +64,20 @@ def scramble_64b66b(data, state=0x3ffffffffffffff):
     return data_out
 
 
+def scramble_pcie(data, state=0xffff, poly=0x9c00):
+    data_out = bytearray()
+    for d in data:
+        b = 0
+        for i in range(8):
+            if state & 1:
+                state = (state >> 1) ^ poly
+                b = b | (1 << i)
+            else:
+                state = state >> 1
+        data_out.append(b ^ d)
+    return data_out
+
+
 async def run_test_scramble(dut, ref_scramble):
 
     data_width = len(dut.data_in)
@@ -75,7 +89,7 @@ async def run_test_scramble(dut, ref_scramble):
 
     block = bytearray(itertools.islice(itertools.cycle(range(256)), 1024))
 
-    scr = scramble_64b66b(block)
+    scr = ref_scramble(block)
     scr_iter = iter(chunks(scr, byte_lanes))
 
     first = True
@@ -108,6 +122,11 @@ if cocotb.SIM_NAME:
         factory.add_option("ref_scramble", [scramble_64b66b])
         factory.generate_tests()
 
+    if cocotb.top.LFSR_POLY.value == 0x0039:
+        factory = TestFactory(run_test_scramble)
+        factory.add_option("ref_scramble", [scramble_pcie])
+        factory.generate_tests()
+
 
 # cocotb-test
 
@@ -128,11 +147,13 @@ def process_f_files(files):
     return list(lst.values())
 
 
-@pytest.mark.parametrize(("lfsr_w", "lfsr_poly", "lfsr_init", "lfsr_galois", "reverse", "data_w"), [
+@pytest.mark.parametrize(("lfsr_w", "lfsr_poly", "lfsr_init", "lfsr_galois", "reverse", "data_w", "self_sync"), [
-            (58,  "58'h8000000001", "'1", 0, 1, 8),
+            (58,  "58'h8000000001", "'1", 0, 1, 8, 1),
-            (58,  "58'h8000000001", "'1", 0, 1, 64),
+            (58,  "58'h8000000001", "'1", 0, 1, 64, 1),
+            (16,  "16'h0039", "'1", 1, 1, 8, 0),
+            (16,  "16'h0039", "'1", 1, 1, 64, 0),
         ])
-def test_taxi_lfsr_scramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois, reverse, data_w):
+def test_taxi_lfsr_scramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois, reverse, data_w, self_sync):
     dut = "taxi_lfsr_scramble"
     module = os.path.splitext(os.path.basename(__file__))[0]
     toplevel = dut
@@ -152,6 +173,7 @@ def test_taxi_lfsr_scramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois,
     parameters['LFSR_GALOIS'] = f"1'b{lfsr_galois}"
     parameters['REVERSE'] = f"1'b{reverse}"
     parameters['DATA_W'] = data_w
+    parameters['SELF_SYNC'] = f"1'b{self_sync}"
 
     extra_env = {f'PARAM_{k}': str(v) for k, v in parameters.items()}